These days the development of digital camera system-making technique result in miniaturization and lightweight, the camera is more and more common for telecommunication handset.
The digital camera is improved to have high performance till 3M pixel, furthermore it is to be improved to commercialize 7M.
As the digital camera is improved to have high performance, various function such as optical zoom, auto focusing and image stabilizing function is adopted to the digital camera. Among the various function auto-focusing function is particularly adapted to the digital camera.
The method is used to convert rotation movement into linear movement by transforming device such as stepping motor or DC motor. However a driving unit is too large, so it is to solve the problem to meet technical evolution which the handset is to be miniaturization and slim.
Therefore, to solve this problem the method is adopted to shift the lens module such as voice coil motor, the driving principle of VCM is disclosed in Korean patent application laid-open No. 2006-0122125.
The method for using VCM can miniaturize space to occupy the driving portion, but there are various problems with realization of auto-focusing function.
It is adopted to open loop control type method which is to control the current to be applied to VCM according to the result of image signal to be transmitted from image sensor module, but in this case there is a problem not to supply clear image to user because the focus is not fitted to subject as a result of success or failure lens module to prompt shift to target position.
It is differ from not only assembly deviation in many articles, but also driving force used to shift lens module (same displacement) owing to self-weigh as shooting angle in same article. It always outputs same signals as same target position not to considerate difference in prior art.
In case the same current to be input lens driving part is controlled as same control signal, above mentioned focus of the subject is not fit because of difference on displacement shift in same article.